package others;

import java.util.Stack;

public class TestOffer09 {
    /**
     * vmware 面试题
     * 剑指 Offer 09. 用两个栈实现队列
     * 用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead操作返回 -1 )
     * 输入：
     * ["CQueue","appendTail","deleteHead","deleteHead"]
     * [[],[3],[],[]]
     * 输出：[null,null,3,-1]
     */
    private Stack<Integer> stack1;
    private Stack<Integer> stack2;


    public TestOffer09() {
        stack1 = new Stack<Integer>();
        stack2 = new Stack<Integer>();

    }

    public void appendTail(int value) {
        stack1.push(value);
    }

    public int deleteHead() {
        if(!stack2.isEmpty()){
            return stack2.pop();
        }else {while(!stack1.isEmpty()){
            stack2.push(stack1.pop());
        }}
        return stack2.isEmpty()? -1 : stack2.pop();
    }

    /**
     * Your CQueue object will be instantiated and called as such:
     * CQueue obj = new CQueue();
     * obj.appendTail(value);
     * int param_2 = obj.deleteHead();
     */
}
